This invention relates to a mobile node, a mobile agent and a network system. More particularly, this invention relates to a control method which assists the movement of a node between an IP (Internet Protocol) network capable of executing communication in accordance with both IP version 4 and an IP version 6 and an IP network capable of executing communication in accordance with only the IP version 4 or an IP network capable of executing communication in accordance with only the IP version 6, a mobile agent, and a network system for assisting the movement of the node.
With a drastic development of small and light-weight nodes and the Internet, the demand for taking out a node from an office or a home to utilize it everywhere has been increased. When the node is moved to other network in the conventional network environment making use of the TCP/IP (Transmission Control Protocol/Internet the information for primarily identifying the node in the Protocol), however, setting of the IP address, which is IP network, must be changed so as to match with the foreign or visiting network environment.
Even if this change of setting of the IP address is automatically mae by utilizing a DHCP (Dynamic Host Configuration Protocol) described in RFC (Request For Comment) 1541 as one of the methods of distributing automatically the IP addresses, there remains the problem that the network connection that has been established already with other nodes by using the IP addresses used in the network before the movement cannot be maintained in succession.
Therefore, methods of assisting the movement of the node between the networks have been devised. A typical among them is a protocol of the third layer (network layer) of an OSI (Open Systems Interconnection) reference model and this protocol pertains to the IP version 4 (hereinafter called the xe2x80x9cIPv4xe2x80x9d) that has gained a wide application in the Internet and the IP version 6 (hereinafter called the xe2x80x9cIPv6xe2x80x9d) the specification of which has now been stipulated so as to solve the problems of address exhaustion in the IPv4. As to these IPv4 and IPv6, xe2x80x9cIP Mobility Support in IPv4xe2x80x9d) (hereinafter called xe2x80x9cMobile IPv4xe2x80x9d) described in RFC2002 and xe2x80x9cMobility Support in IPv6xe2x80x9d) (hereinafter called xe2x80x9cMobile IPv6xe2x80x9d) described in IETF (Internet Engineering Task Force) draft (the latest version of which is xe2x80x9cdraft-ietf-mobile-ip-ipv6-02.txtxe2x80x9d) are examples of the known references.
Incidentally, the term xe2x80x9cIPv4xe2x80x9d used in this specification designates an IP address having an address length of 32 bits while the term xe2x80x9cIPv6xe2x80x9d designates an IP address having an address length greater than 32 bits.
By making use of these Mobile IPv4 and Mobile IPv6, a user can execute communication in the same way before the movement of the node even when the node is moved to another network, without the necessity for changing the IP address of the node or cutting off the network connection that has already been established with other node before the movement.
Incidentally, the term xe2x80x9cnodexe2x80x9d used in this specification designates all those devices which have an IP address and execute communication by utilizing the IP, such as a PC (Personal Computer), a WS (Work Station), a router, and so forth.
Generally, it is assumed that the movement from the IPv4 to the IPv6 is effected gradually and all the networks do not utilize at once the IPv6. In the mean time, therefore, there exist a network (hereinafter called the xe2x80x9cIPv4 networkxe2x80x9d) comprising only those nodes which execute communication by utilizing only the IPv4 (hereinafter called the xe2x80x9cIPv4 nodesxe2x80x9d), a network (hereinafter called the xe2x80x9cIPv6 networkxe2x80x9d) comprising only those nodes which execute communication by utilizing only the IPv6 (hereinafter called the xe2x80x9cIPv6 nodexe2x80x9d) and a network (hereinafter called the xe2x80x9cIPv4/v6 networkxe2x80x9d) comprising those nodes which execute communication by utilizing both of IPv4 and IPv6 in mixture (hereinafter called the xe2x80x9cIPv4/v6 nodexe2x80x9d), the IPv4 nodes and the Ipv6 nodes.
To beginning with, let""s consider the case where the Ipv4/v6 network is the one that supports both of Mobile IPv4 and Mobile IPv6. In the Mobile IPv4, messages are exchanged between a mobile node moving between the networks and a mobile agent (hereinafter called the xe2x80x9cIPv4 mobile agentxe2x80x9d) for assisting the movement of the mobile node which executes communication by utilizing the IPv4, in accordance with the Mobile IPv4 procedures. Similarly, in the Mobile IPv6, messages are exchanged between a mobile node moving between the networks and a mobile agent (hereinafter called the xe2x80x9cIPv6 mobile agentxe2x80x9d) for assisting the movement of the mobile node that executes communication by utilizing the IPv6, in accordance with the Mobile IPv6 procedures.
Let""s consider the case where the IPv4/v6 mobile node supporting both of Mobile IPv4 and Mobile IPv6 inside the IPv4/v6 network moves to another IPv4/v6 network. Because the foreign IPv4/v6 network can execute communication by utilizing both of IPv4 and IPv6, the IPv4/v6 mobile node can exchange the messages with both of the IPv4 mobile agent and the IPv6 mobile agent on the network in accordance with the procedures of the Mobile IPv4 and the Mobile IPv6. Therefore, the movement of this IPv4/v6 mobile node between the networks is supported by both of the Mobile IPv4 and the Mobile IPv6. In consequence, the IPv4/v6 mobile node that has moved to the foreign network can successively execute communication without changing setting of the IP address and without cutting off the network connection that has been established already with other IPv4 node or the IPv6 node before its movement by utilizing the IPv4 or IPv6. It can also execute afresh communication with other node by utilizing the IPv4 and the IPv6.
Next, let""s consider the case where the IPv4/v6 mobile node moves from the IPv4/v6 network to the IPv4 network which can execute communication in accordance with only the IPv4 and supports the Mobile IPv4. In this case, since communication by utilizing the IPv4 is possible between the IPv4/v6 mobile node and the IPv4 mobile agent, the assistance of movement of this mobile node between the networks by the Mobile IPv4 can be made. Therefore, the IPv4/v6 mobile node can execute communication successively after the movement without cutting off the network connection that has been previously established already with other IPv4 node by utilizing the IPv4. The mobile node can also execute communication afresh by utilizing the IPv4.
However, the mobile node cannot execute communication by utilizing the IPv6 on the IPv4 network and consequently, the exchange of the message on the IPv4 network in accordance with the Mobile IPv6 procedure becomes impossible between the IPv4/v6 mobile node and the IPv6 mobile agent. In other words, the assistance of the movement of the mobile node to the IPv4 network in accordance with the Mobile IPv6 becomes impossible and the IPv4/v6 mobile node that has moved to the IPv4 network cannot maintain the network that has been established already with other IPv6 node by utilizing the IPv6 before the movement and consequently, cannot execute communication. This mobile node cannot execute afresh communication with other node on the IPv4 network by utilizing the IPv6, either.
Similarly, let""s consider the case where the IPv4/v6 mobile node moves from the IPv4/v6 network to the IPv6 network which can execute communication by utilizing only the IPv6 and supports the Mobile IPv6. In this case, too, the IPv4/v6 mobile node cannot execute communication by utilizing the IPv4 on the IPv6 network. In consequence, the exchange of the message in accordance with the Mobile IPv4 procedure is not possible on the IPv6 network between the IPv4/v6 mobile agent and the IPv4 mobile agent, so that the assistance of the movement of this mobile node to the IPv6 network in accordance with the Mobile IPv4 becomes impossible on the IPv6 network.
It is therefore an object of the present invention to provide a mobile node, a mobile agent and a network system which can successively maintain the network connection the IPv6 that has been established already by utilizing the IPv6 before the movement when the IPv4/v6 mobile node moves from the IPv4/v6 network to the IPv4 network, and which can also execute afresh communication by utilizing the IPv6.
It is another object of the present invention to provide a control method of a mobile node, a mobile agent and a network system for assisting the movement, which can execute communication by utilizing the IPv4 between an IPv4/v6 mobile node and other IPv4 node even when the IPv4/v6 mobile node moves from an IPv4/v6 network to an IPv6 network, without changing at all existing IPv6 mobile agents and existing IPv4/v6 mobile agents and without changing setting of the address of the IPv4/v6 mobile node.
According to one aspect of the present invention, there is provided a mobile node including IPv4 (Internet Protocol version 4) processing means for executing services in accordance with the IPv4, IPv6 (Internet Protocol version 6) processing means for executing services in accordance with the IPv6, and communication processing means for executing transmission/reception control of packets to and from networks, and moving between IP networks, wherein the mobile node further comprises movement registration processing means for adding an IPv4 header (IP header used for the IPv4), in which the IPv4 address of a mobile agent is set as a foreign address and the IPv4 address of the mobile node usable in a foreign IPv4 network is set as a home address, to a message used for the IPv6 for registering the movement to a mobile agent connected to the IPv4/v6 network to assist the movement of the mobile node, and transmitting the message, when this mobile node moves from the IPv4/v6 network (a network capable of executing communication by utilizing both of the IPv4 and the IPv6) to an IPv4 network (a network capable of executing communication by utilizing only the IPv4).
In the mobile node according to the aspect of the invention described above, the IPv4 header is added to the message used for the IPv6 and the message is then transmitted. Therefore, the message to be used for the IPv6 can be substantially transmitted from the foreign IPv4 network, and the information necessary for the network connection utilizing the IPv6 can be registered to the mobile agent.
According to another aspect of the present invention, there is provided a mobile agent including IPv4 processing means for executing services in accordance with an IPv4, IPv6 processing means for executing services in accordance with an IPv6 and communication processing means for executing transmission/reception control of packets to and from networks, and moving between the networks, wherein the mobile agent further comprises packet transmission processing means for generating an IPv4 encapsulated IPv6 packet by adding an IPv4 header, in which the IPv4 address of the mobile agent is set as a foreign address and the IPv4 address of a mobile node usable in a foreign IPv4 network is set as a home address, to an IPv6 packet (packet used for the IPv6) to be transmitted to other node, and transmitting the IPv4 encapsulated IPv6 packet so generated.
In the mobile agent according to the aspect of the invention described above, after the IPv4 header is added to the IPv6 packet, the packet is transmitted. Therefore, the IPv6 packet can be transmitted substantially from the foreign IPv4 network.
According to still another aspect of the present invention, there is provided a mobile node including IPv4 processing means for executing services in accordance with the IPv4, IPv6 processing means for executing services in accordance with the IPv6 and communication processing means for executing transmission/reception control of packets to and from networks, and moving between the networks, wherein the mobile node further comprises movement detection means for detecting whether the mobile node has moved from the network in which a mobile agent used by this mobile node exists to another IPv4 network or to an IPv6 network (network capable of executing communication by utilizing only the IPv6) or to an IPv4/v6 network, and movement status management means for managing the movement status so detected.
Since the mobile node according to this aspect of the invention automatically detects the kind of the network in which the mobile node itself exists at present and manages itself, the necessity for adding an IPv4 header to the message used for the IPv6 or the IPv6 packet can be judged appropriately.
According to still another aspect of the present invention, there is provided a mobile agent for assisting the movement of a mobile node executing communication by utilizing an IPv6, including IPv4 processing means for executing services in accordance with an IPv4, IPv6 processing means for executing services in accordance with the IPv6 and communication processing means for executing transmission/reception control of packets to and from networks, wherein the mobile agent further comprises mobile node management means for managing the IPv4 address of a mobile node usable in a foreign IPv4 network when receiving a message for use in the IPv6 for registering the movement, to which an IPv4 header transmitted from the mobile node to the IPv6 network to the mobile agent when the mobile agent moves to the IPv4 network is added, and movement assistance processing means for adding an IPv4 header, in which the IPv4 address of the mobile node usable in a foreign IPv4 network is set as a foreign address and the IPv4 address of the mobile agent is set as a home address, to the message used for the IPv6 to permit registration of the movement to the mobile node, and transmitting the message.
In the mobile agent according to the aspect of the invention described above, after the IPv4 header is added to the message used for the IPv6 and then the message is transmitted. Therefore, the message used for the IPv6 can be transmitted substantially to the mobile node that is moving to the IPv4 network.
According to still another aspect of the present invention, there is provided a mobile agent for assisting the movement of a mobile node executing communication by utilizing the IPv6, including IPv4 processing means for executing services in accordance with the IPv4, IPv6 processing means for executing services in accordance with the IPv6 and communication processing means for executing transmission/reception control of packets to and from networks, wherein the mobile agent further comprises transfer-to-other node processing means for deleting the IPv4 header when receiving an IPv4 encapsulated IPv6 packet transmitted by the mobile node, and transmitting again the IP packet so taken out to the network.
In the mobile agent according to the aspect of the invention described above, after only the IPv6 packet is taken out from the IPv4 encapsulated IPv6 packet, the IPv6 is again transmitted. Therefore, the IPv6 packet can be transmitted substantially from the mobile node, that is moving to the IPv4 network, to the node on the IPv6 network or on the IPv4/v6 network.
According to still another aspect of the present invention, there is provided a mobile agent for assisting the movement of a node executing communication by utilizing the IPv6, including IPv4 processing means for executing services in accordance with the IPv4, IPv6 processing means for executing services in accordance with the IPv6 and communication processing means for executing transmission/reception control of packets to and from networks, wherein the mobile agent further comprises transfer-to-other node processing means for generating an IPv4 encapsulated IPv6 packet by adding an IPv4 header, in which the IPv4 address of a foreign node usable in a foreign IPv4 network is set as a foreign IPv4 address and the IPv4 address of the mobile agent is set as a home IPv4 address, to the received IPv6 packet when receiving this IPv6 packet transmitted by other node to the mobile node that has moved to the IPv4 network, and for transmitting this IPv4 encapsulated IPv6 packet.
In the mobile agent according to the aspect of the invention described above, after the IPv4 header is added to the IPv6 packet, the IPv6 packet is transmitted. Therefore, the IPv6 packet can be transmitted substantially from the node on the IPv6 network or on the IPv4/v6 network to the mobile node that is moving to the IPv4 network.
According to still another aspect of the present invention, there is provided a network system in which an IPv4/v6 netwirj and an IPv4 network are connected with each other by a connecting device or by the connection device and a third network, wherein the mobile agent according to the fourth, fifth or sixth aspect is provided on the IPv4/v6 network and the mobile node according to the first, second or third aspect is provided on the IPv4/v6 network or on the IPv4 network.
The network system according to the aspect described above can successively keep the network connection, which utilizes the IPv6 and has been already established before the movement of the IPv4/v6 node, when the IPv4/v6 node moves from the IPv4/v6 network to the IPv4 network, and can execute afresh communication by utilizing the IPv6.
According to still another aspect of the present invention, there is provided a method of controlling a mobile node by a mobile agent in a network system in which a first IP network capable of executing communication in accordance with first and second kinds of IPs and a second IP network capable of executing communication in accordance with only the first kind of IP, so that the mobile node capable of executing communication in accordance with the second kind of IP can communicate with other node belonging to the first IP network in accordance with the second kind of IP when the mobile node moves from the first IP network to the second IP network, which method comprises the steps of adding a first kind of IP header, in which the IP address of a second mobile agent belonging to the second IP network in accordance with the first kind of IP is set as a foreign address by the first mobile agent belonging to the first IP network and the IP address of the first mobile agent in accordance with the first kind of IP is set as a home address, to an IP packet transmitted in accordance with the second kind of IP from other node to the mobile node, and transmitting the IP packet to the second mobile agent; and deleting the first kind of IP header by the second mobile agent and transmitting the IP packet to the mobile node.
On the other hand, the IP packet may be transmitted to other node by adding the first kind of IP header, in which the IP address of the first mobile agent in accordance with the first kind of IP is set as a foreign address by the second mobile agent and the IP address of the second mobile agent in accordance with the first kind of IP is set as a home address, to the IP packet in accordance with the second kind of IP transmitted from the mobile node to other node, transmitting this IP address to the first mobile agent, deleting the first kind of IP header by the first mobile agent and then transmitting the IP packet to other node.
Alternatively, it is possible to employ a method comprising adding the first kind of IP header, in which the IP address of the first mobile agent in accordance with the first kind of IP is set as a foreign address by the second mobile agent and the IP address of the second mobile, agent in accordance with the first kind of IP is set as a home address, to a movement registration request message in accordance with the second kind of IP that is received from the mobile node, transmitting this message to the first mobile agent, adding the first kind of IP header, in which the IP address of the second mobile agent in accordance with the first kind of IP is set as a foreign address by the first mobile agent and the IP address of the first mobile agent in accordance with the first kind of IP is set as a home address, to a message in accordance with the second kind of IP for permitting the movement, and transmitting this message to the second mobile agent.
The present invention provides also a network system for assisting the movement of the mobile node, having the features described above.
Furthermore, the present invention provide the first and second mobile agents for assisting the movement of the mobile node, having the features described above.